Spinach Growers Value Host Resistance and Synthetic Fungicides in the Fight against Downy Mildew

Abstract

California spinach growers struggle to manage spinach downy mildew disease. The disease is especially difficult in the organic crop, which currently relies on resistant varieties to maintain disease-free crop. Alternative control measures are available, but it is not clear how growers perceive the efficacy of these methods. It is also not clear who growers contact to find out information on spinach downy mildew disease management. In this study, we conducted an online survey of people involved in spinach production, asking about their beliefs in the efficacy of different control methods and who they contact frequently to discuss spinach downy mildew control. We found that respondents were most positive about the efficacy of resistant varieties and synthetic pesticides, with much lower perceived efficacy for the practices of disking diseased fields, roguing diseased plants, and organic pesticides. Growers most frequently contacted pest control advisors (PCAs) about management strategies for spinach downy mildew. These results suggest that respondents are most confident about the efficacy of resistant varieties and synthetic pesticides and may be hesitant to adopt new control strategies like organic pesticides. The results also suggest that future extension efforts can be focused on PCAs to reach the most stakeholders with up to date research on downy mildew control.

Survey of Spinach Downy Mildew Management Practices and Communication Network

“…This proportion is lower than those found in other studies. Choudhury et al (2016) found that 31.7% of fields surveyed for spinach downy mildew had disease incidence greater than 0.1%. Our participant's estimate for disease affected fields may be lower because they do not count fields that had only small patches of disease, or that they were unable to detect disease due to insufficient surveillance.…”

“…In the future, surveys can be conducted to explore producer's willingness to pay and adopt alternative management practices, like resistant seeds developed with CRISPR technology (Kock et al 2019), spore trapping (Choudhury et al 2016a), mixes of resistant and susceptible varieties (Choudhury et al 2016b), oospore seed thresholds (Choudhury et al 2017a), and organic pesticides (Choudhury et al 2015a;Choudhury et al 2017b). These studies could be conducted online or in person.…”

“…As new races of the pathogen overcome the resistant varieties, growers need to heavily rely on new varieties being bred by a relatively small portion of seed producers (Feng et al 2018). Although some organic fungicides on the market are available and show some control of disease, they do not control to economic levels and need to be supplemented with resistant varieties for full effect (Choudhury et al 2015a;Choudhury et al 2017b).…”

Crop Residue Management Strategies to Reduce Nitrogen Losses during the Winter Leaching Period after Autumn Spinach Harvest

“…Vegetable crop residues are usually incorporated into the soil shortly after the harvest in order to minimize the risk of infection by plant pathogens such as damping-off diseases and downy mildew in spinach crop rotations [9,19,20]. However, spinach crop residues are characterized by a low carbon (C) to N ratio which accelerates net mineralization and nitrification after incorporation into the soil.…”